Bistable device



July 19, 1966 G. w. GOODRICH 3,262,008

BISTABLE DEVI CE Filed Nov. 12, 1963 2 Sheets-Sheet l SOURCE DIRECT W VOLTAGE SOURCE +IOOV l0 6 s 9 E PULSE V SOURCE l7 I000 V m g-E uoo v VOLT {SOURCE 5000 V I5 Fig. 2

INVENTOR.

GEORGE W. GOODRICH July 19, 1966 3, w GOODRICH 3,262,008

BIS'IABLE DEVICE Filed Nov. 12, 1963 2 Sheets-Sheet 2 INVENTOR. GEORGE W. GOODRICH United States Patent C) 3,262,008 BISTABLE DEVICE George W. Goodrich, Oak Park, Mich., assignor to The Bendix Corporation, Southfield, Mich., a corporation of Delaware Filed Nov. 12, 1963, Ser. No. 322,741 Claims. (Cl. 315-12) This invention relates to bistable devices and more particularly, to matrices of bistable devices by means of which images may be displayed or operated upon.

Visual data plotting display systems in present use are relatively bulky instruments possessing inherent limitations to accurately produce and store bright visual images over extended time intervals. To overcome perhaps the greater limitations of such systems, i.e., the inability to store picture elements and the inability to produce pictures of high trace brightness, photographic techniques are customarily employed.

In accordance with this invention, a bistable device useful as an indicating element for a visual data plotting display system is formed from a suitable arrangement of channel electron multiplying and channel dynode members. This invention, therefore, has made it possible to produce such a system having substantial advantages over present systems in that the device is physically small and simple to construct; it is electrically activated to write and erase; no moving parts are required; a particular element within the display matrix may be precisely sedata display systems hereinbefore stated may be surmounted and additional advantages may be procured.

An object of this invention is to provide a bistable device.

Another object of this invention is to provide a mosaic bistable device.

A further object of this invention is to provide an indicating bistable device as an element for a visual data plotting display board.

A still further object of this invention is to provide an image filter for use in opticalcomputers in which the transmission of an input image can be gated on or off on a pointby-point basis for all or a number of image elements.

Other objects and advantages will become apparent from the following detailed description and from the appended claims and drawings:

In the drawings:

FIGURE 1 is a perspective view schematically illustrating one embodiment of a bistable device in which a channel electron multiplying member and a single channel dynode member are employed in tandem relationship.

FIGURE 2 is a plan view of another embodiment of a bistable device in which a channel electron multiplying member is followed by two channel dynode members for the formation of rows and columns in a matrix data display system.

FIGURE 3 is a perspective view illustrating a number of bistable devices of the type shown in FIGURE 2 used to form a matrix suitable for visual data displays.

Referring now to FIGURE 1, reference numeral 2 denotes a sealed vacuum envelope, which may be of glass, enclosing: an electron emitter 4, such as a radioactive electron source, disposed to introduce a sustained electron current to a channel multiplying member 6; a channel dynode member 8, which may be referred to as a secondary electron emitter, positioned to regulate signal current emanating from said member 6; an auxiliary electrode 10 which controls the electric field near the output end of the dynode member 8; a phosphor screen 12 which displays a light image of signal current received from said member 8; a direct voltage source 14 by means of which biasing voltages of -ll00 volts, l000 volts, 0 volts, +10 volts, volts, and +5000 volts are applied respectively, to the electron emitter 4, the input of channel 6, the output of channel 6, the channel dynode 8, the electrode 10, and the phosphor screen 12; and a pulse source 16 which transmits a write or erase signal to the dynode member 8.

Due to the potential of 1000 volts impressed across the channel multiplying member 6, current flows through the inner resistive surface of the multiplier producing an electric field conducive to sustain electron multiplication. These multipliers are fully disclosed in co-pending US. application, Serial No. 23,574, filed April 20, 1960 by W. C. Wiley and myself, now Patent 3,128,408. The potential of 100 volts between the electron emitter 4 and the input of the channel 6 provides electrons from the source 4 with a sufiicient energy gain to dislodge secondary electrons from the inner surface of the multiplying member 6 and the stage is set for sustained electron emission within the multiplier which subsequently produces a continuous cloud of electrons to emanate from said member 6. Since the channel dynode member 8 is only at a bias potential of +10 volts, the continuous cloud of electrons emanating from the multiplying memher 6 will merely be absorbed by the surface of the dynode. No secondary electrons are produced because of an insufficient energy gain.

However, when an adequately high positive pulse, for example +50 volts, is applied to dynode 8 from the pulse source 16, a field condition is created within the dynode 8 such that the cloud of electrons emanating from the multiplying member 6 acquire energy suificient to release secondary electrons from the inner surface of the dynode, and this current proceeds through the field limiting electrode 10 to the phosphor screen 12 where a light image is formed.

Thus, when the dynode member 8 of the bistable device of FIGURE 1 receives a sufficiently high positive signal pulse a visual image is written upon the screen 12 which continues to be written until the dynode member 8 is given a reverse polarity of sufficient magnitude, for example, 50 volts. The image continues to be written even though the positive signal is removed because the dynode potential remains positive due to the withdrawal of electrons from its surface during secondary emission.

Of course, since the positive potential of the dynode would increase until limited by the potential of the phosphor screen 12, with corresponding stoppage of electron transport to the screen, an auxiliary electrode 10 is utilized to limit the potential of the dynode 8 at a value much less than that of the phosphor screen; for example, +100 volts, and electron transport to the screen is preerved.

Conversely, upon the application of a sufiicient negative signal pulse, for example, 50 volts, to dynode 8 from the pulse source 16, a field condition is created within the dynode which either returns the electrons to the multiplier 6, or collects them, causing the current to flow through the dynode 8 in such a fashion that the potential of said dynode will remain negative. Thus, electrons emanating from the multiplying member 6 will not be allowed to proceed through the dynode 8 and no image will be Written on the phosphor screen 12.

It can readily be appreciated that if a matrix of bistable devices is formed, pictures can easily be produced by pulsing the appropriate dynodes 8 on or off. For example, this pulsing may be accomplished by means of capacitive coupling with an external probe or by electron beam-scanning techniques.

Another embodiment of the bistable device is shown in FIGURE 2, wherein first and second channel dynode members are employed. The second dynode 9 disposed nearest to the phosphor screen 12 can be biased somewhat more positively than the first to aid operation. For example, volts and +15 volts can be applied respectively to dynodes 8 and 9 from the direct voltage source 15 as shown in the figure. Now, unless both dynodes 8 and 9 are simultaneously pulsed from a pulse source 17 in the positive direction, no current will flow to the phosphor screen 12. Thus, as shown in FIGURE 3, it lead wires to corresponding dynodes from each bistable device in a matrix are brought out to correspond with horizontal row positions and the lead wires to the other dynodes are brought out to correspond with vertical row positions, the bistable device will activate Whenever appropriate signal voltages are applied to these positions along the sides of the matrix. In this way, the bistable device may be employed, for example, as an element for a visual data plotting display board or as an element for an image filter for use in optical computers.

In FIGURE 3, a plurality of bistable devices of the type disclosed in FIGURE 2 is utilized to form a matrix for the visual presentation of coordinate information. As shown in the figure, corresponding dynodes of each bistable device are grouped into two separate arrays, a first array containing four rows of commonly connected dynodes 8, and a second array containing four rows of commonly connected dynodes 9, with each row of the respective arrays separated from contiguous rows by a thin insulative strip 18. The rows of the first and second arrays are designated respectively by numerals 22, 24, 26, 28 and 30, 32, 34, 36, with each row of the first array being orthogonally disposed relative to the rows of the second array. Since each dynode in a given row is commonly connected to adjacent dynodes by means of metallic electrodes 20, only one lead wire is required per row to distribute both the direct dynode bias voltage and the pulsed signal voltage from sources as shown in FIG- URE 2.

To illustrate the operation of coordinate selection assume two voltage pulses are applied to the matrix, one of such pulses being received by row 22 of the first array and the remaining pulse being received by row 30 of the second array. As a result, all dynodes 8 within row 22 are activated to receive electrons from corresponding members 6, and all dynodes 9 within row 30 are activated to receive electrons from corresponding dynodes 8. However, only one coordinate of the matrix will be activated to display an image upon the phosphor screen since only one coordinate will have both of its dynodes 8 and 9 activated, namely, coordinates 22-30.

Thus, the matrix will operate to display a visual image point upon the screen whenever both dynodes 8 and 9 of a particular device within the matrix are selected to receive signal pulses, and this selection will be made, for example, by standard computer selection techniques.

In the above described embodiments of the bistable device, the initiating current is produced by an electron emitter 4, such as a radioactive material. However, there is an alternative method for generating the initiating current for the multiplying member 6. This method ofiers an advantage in that no radioactive materials or thermionic emitters are required. It Works on the principle that if the residual gas pressure inside the mutiplying member 6 is high enough, a regeneration phenomenon is established which causes the multiplier to discharge electrons in the absence of any outside current source.

The mechanism of this action is believed to be as follows: In the presence of a gas within the multiplying member, some of the thermal electrons which are proceeding through the member in a normal fashion collide with gas molecules with sufficient energy to cause ionization. The positive ions formed proceed backwards through the multiplying member in a direction opposite to the normal fiow of electrons. Eventually they strike the wall of the member where a certain fraction of the ions cause the emission of electrons. These electrons, in turn, are increased in number as they progress through the multiplying member in the normal direction and they again make more ions. In this fashion, regeneration occurs which, under proper multiplying member operating parameters and gas pressure, results in a discharge of sustained electron current.

Although this invention has been disclosed and illustrated with reference to particular applications, the principles involved are susceptible of numerous other applications which will be apparent to persons skilled in the art.

Having thus described my invention, I claim:

1. A bistable device comprising means for producing particles,

:a dynode disposed to receive the particles,

said dynode having secondary electron emissive properties,

means for applying a first pulse to the dynode to produce secondary electrons upon receipt of the particles, said last means for applying a second pulse to the dynode to stop production of secondary electrons,

and a collector disposed to receive the secondary electrons produced by the dynode.

2. A bistable device as set forth in claim 1 comprising in addition an electrode disposed between the dynode and the collector,

and means for applying a biasing voltage to the electrode to limit the potential build-up of said dynode.

3. A bistable device comprising means for producing particles,

a channel electron multiplying member disposed to receive and amplify said particles,

a first channel dynode member disposed to receive electrons emerging from said channel multiplying memher,

a second channel dynode member disposed to receive electrons emerging from said first channel dynode member,

means for applying biasing voltages to said members,

means for applying a first pulse to each of said first and second dynode members to produce secondary electrons upon receipt of electrons, and for applying a second pulse to each of said first and second dynode members to stop production of secondary electrons,

and a collector disposed to receive the electron response from said second channel dynode member.

4. A bistable device as set forth in claim 3 comprising in addition an electrode disposed between said second channel dynode member and the collector,

and means for applying a biasing voltage to the electrode to limit the potential build-up of said dynode.

5. A device for displaying images comprising a plurality of bistable devices as described in claim 4 arranged in a matrix,

wherein first and second dynodes of each device are respectively disposed in first and second arrays,

the rows of said first array being orthogonally oriented to the rows of said second array,

means for applying a first and second pulse to the dynodes of said first and second arrays,

means for selecting the dynode members of said first and second arrays to receive said first and second pulses,

and means for converting the response of selected bistable devices into visual images.

References Cited by the Examiner UNITED STATES PATENTS 2/ 1947 Goodall SIS-5.11

DAVID G. REDINBAUGH, Primary Examiner.

T. A. GALLAGHER, Assistant Examiner. 

